Carbon nanotubes (CNTs) have recently captured attention as novel materials for nanoelectronic sensors due to their ability to achieve better sensitivity and accuracy in these devices. Up until now, the majority of investigations have focused on experimental studies for sensors. Therefore, there is lack of analytical models comparative to experimental investigations. The proposed model employs a CNT-based field effect transistor (CNT-FET) scheme to model the transport parameters of the CNT-based gas sensor. The CNT conductance is affected on exposure to the target analyte – NH3 gas molecules. The NH3 gas concentration is absorbed on the CNT surface after a chemical reaction between the CNT and NH3. This modulates the current-voltage (I-V) characteristics and conductance of the CNT-based gas sensor. The I-V characteristics of the CNT-based sensor have been proposed as a criterion to detect the effect of gas absorption. Finally, the proposed model was compared with experimental investigation for validation.